This invention relates to colorless photocurable compositions, which produce colored three-dimensional solid objects by stereolithographic processes. More particularly, this invention relates to photocurable compositions comprising (1) photocurable monomers, oligomers, dendrimers and polymers, (2) photoinitiators, (3) color generating compounds and optionally, (4) soluble reactive silsesquioxanes (POSS).
U.S. Pat. Nos. 4,575,330 and 4,929,402 described a stereolithographic process, which can be employed to build up a predetermined three-dimensional object by forming series of layers of polymerized solids. The disclosure of U.S. Pat. Nos. 4,576,330 and 4,929,402 is incorporated herein by reference. During stereolithographic processing, a cross-section of the solid is traced out on the surface of a bath of liquid acrylate containing polymer precursors under the direction of a computer controlled system which causes the liquid to be exposed to a form of photoradiation such as ultraviolet or visible lasers. Exposure to photoradiation causes the liquid to polymerize and harden. After each polymerized layer is formed and solidified, it is lowered in the bath so that a new solid layer can be formed on top. This technology has been found very useful in prototyping applications, since the prototypes can be rapidly and accurately built from computer-generated graphic models.
Photocurable compositions currently used for stereolithography are known in the art. Typical photocurable compositions for application in stereolithography may contain (1) photocurable monomers, oligomers and polymers, (2) photoinitiators and (3) optional insoluble organic or inorganic fillers, which are dispersed in the composition. U.S. Pat. Nos. 5,510,226; 5,705,316 and 5,705,116 also teach to prepare photocurable compositions containing monomers and oligomers, which have functional groups such as acrylate, methacrylate, epoxy and vinyl ether.
U.S. Pat. Nos. 5,629,133 and 5,639,413 teach photocurable compositions comprising siloxane monomers, oligomers and polymers that contain epoxy functional groups.
U.S. Pat. Nos. 5,863,486 and 5,855,837 teach photocurable compositions containing inorganic fillers such as inorganic particles, whiskers, E-glass fibers, woven glass fibers, and glass beads dispersed in the photocurable mixtures.
U.S. Pat. No. 6,036,910 teaches liquid photocurable resin composition for stereolithography, which comprises a photopolymerizable compound, a photopolymerization initiator and a colorant. The photocurable composition of this prior art contains between 0.1 and 10% by weight of photopolymerization initiator and 0.05 to 0.5% by weight of the colorant. The photopolymerizable compound is in an amount of the balance, based on the total weight of these components. The photocurable composition is liquid at normal temperature.
The inventors of this invention have also found that the presence of a colorant considerably reduced the shaping speed of the stereolithographic process due to the photoradiation absorption of the colorant. Moreover, the presence of colorant was also found to deteriorate drastically the mechanical and thermal properties of the resulting three-dimensional object.
Photocurable compositions disclosed in the above prior art do not provide desired colors for the resulting solid objects. They do not provide an image print-out during stereolithography so that the three-dimensional object may be seen as it is being made. They do not provide shelf-life and pot-life color indicators. They also suffer by high degree shrinkage during photopolymerization resulting in considerable distortion in the shape of the final objects. They are relatively unstable during operation due to the settlement of the filler particles. Furthermore, the stereolithographic objects obtained from the traditionally used photocurable compositions do not have a sufficiently high glass transition temperature (Tg) enough to withstand functional testing as engine parts or subsequent treatment processes such as drilling, machining and sanding.
Therefore, the object of this invention is to provide photocurable compositions for application in stereolithography to produce desirable colored, three-dimensional solid objects with fast stereolithographic shaping speed, non-settlement of insoluble filler particles, low degree of distortion and superior thermal stability and superior mechanical properties. Furthermore, the object of this invention is to provide photocurable compositions for application in stereolithography that produce color image print-outs during stereolithography and in-situ shelf-life indicators.
This invention relates to colorless liquid photocurable compositions for use in the production of desirable colored three-dimensional solid objects by stereolithography. In general terms, the present invention provides a photocurable resin composition for stereolithography comprising (a) a photocurable component, liquid at room temperature and comprising a photopolymerizable substance selected from monomers, oligomers, dendrimers and polymers and mixtures thereof, (b) at least one photoinitiator compound, and (c) at least one photoactivated color generating compound. The resin composition of the present invention may also comprise functionalized reactive silsesquioxanes (POSS).